TOKYO—Sony Corp.'s shares fell 11.1% in Tokyo trade, wiping out more than $2 billion in market value, after the Japanese electronics maker reported weak quarterly results and cut its profit forecast for the year by 40%.

The poor numbers throw Sony's turnaround strategy into doubt and are a black eye for Kazuo Hirai, who became chief executive last year. He had vowed to pull the company out of a prolonged slump that began when its...